The Wolfe Classification System which is based on the proportion of adipose, ductal and dysplastic tissues seen on mammograms divides the parenchymal patterns into 4 classes with varying risks of developing future breast cancer. Some 40 articles have appeared in the literature since its introduction in 1976, with supporting and contradicting results. Beahr's working group to evaluate Breast Cancer Detection Demonstration Projects (BCDDP) believed it was of sufficient interest to recommend evaluation in the BCDDP population. The differences in the literature appear to relate to the differences between prevalent and incident cancers, age over- and under-50, referred and screening populations, and time after the original negative mammogram as well as the biostatistical methodology. This case-control study considers these factors and also inter-relations with other risk factors. In the first 3 years, the ability of radiologists to classify mammograms according to Wolfe was tested and found satisfactory. METHODOLOGY: The screening populations of 4 BCDDPs (40,000 women) are being contacted annually by phone or letter to identify newly developing breast cancers and update other information. 95% accountability has been obtained. Data is collected on traditional historical risk factors, and in the case of new cancers, tumor type, size, involvement of lymph nodes and presence of calcifications. The pathology reports of all cancers are reviewed. The mammograms from the first year's screenings are mixed with 2 randomly selected "control" mammograms and classified blindly by group radiologist. At the end of this grant period, approximately 680 incident cancers, 220 prevalent cancers and 35 with previous mastectomies will have been evaluated in this case-control study. LONG TERM OBJECTIVES: To evaluate the Wolfe Classification System, its inter-relation with other risk factors, and its usefulness in predicting the future development of breast cancer. The scientific disciplines involved include: radiology, biostatistics, epidemiology and public health and community medicine.